The present invention relates to an optical disk recording apparatus and, more particularly, to an optical disk recording apparatus having a structure for calibrating an optimum recording power when data is recorded on an optical disk.
When data is recorded on a write-once optical disk or the like, in order to obtain stable recording quality, trial writing is performed in a power calibration area on the disk prior to recording, by using plural different recording power values. Then, the area in which the trial writing is performed is reproduced to detect asymmetry of reproduction signals (RF signals), whereby an optimum recording power at the recording is set.
Usually, trial writings can be performed one hundred times in a power calibration area of a write-once optical disk. Therefore, consumption of the calibration area should be reduced. Conventionally, the consumption of the calibration area has been reduced in the following way.
When the trial writing is performed once and an optimum recording power is detected, the detected optimum recording power is stored in a memory in an optical disk recording apparatus, together with a disk identification code for identifying the disk. In case of write-once optical disks, information of a disk in process of recording is held in a PMA (program memory area) of the disk, where a disk identification code for identifying each disk can also be recorded.
When additional recording is performed, the disk identification code is read out from the PMA, while the optimum recording power corresponding to the disk identification code is read out from the memory in the optical disk recording apparatus. Then, additional recording is performed using the readout optimum recording power. Thereby, even if the additional recording is performed after the disk is taken out and then reinserted, or the power is turned off and then turned on, recording can be performed without performing the trial writing again, thereby reducing the consumption of the calibration area.
As an example, Japanese published patent Hei. 6-349066 discloses a recording laser power setting apparatus which can obtain an optimum recording laser power corresponding to each CD-R disk
However, the above-mentioned conventional structure in the optical disk recording apparatus, for reading out the optimum recording power corresponding to each disk from the memory therein, to perform additional recording has the following problem. Due to changes with time in a pickup in the optical disk recording apparatus, particularly dirt or dust accumulated in the pickup, the optimum recording power changes. Consequently, if recording is performed using the optimum recording power stored in the memory, the recording quality is deteriorated.
The present invention is made to solve the above-mentioned problem, and it is an object of the present invention is to provide an optical disk recording apparatus which can reduce consumption of the power calibration area, as well as cope with changes with time in a pickup.
Other objects and advantages of the present invention will become apparent from the detailed description and a specific embodiment described is provided only for illustration since various additions and modifications within the spirit and scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a method of the present invention, the above object can be achieved by checking whether there is a change in an optimum recording power for each disk stored in a memory in an optical disk recording apparatus prior to additional recording on an optical disk, deciding whether desired recording quality can be obtained if the additional recording is performed using the stored optimum recording power, and when it is decided that some problems occur if the stored optimum recording power is used, performing trial writing again to set a new optimum recording power.
An optical disk recording apparatus according to a first aspect of the present invention comprises: an optimum recording power setting unit for obtaining an optimum recording power of a laser diode when data is recorded on an optical disk, by performing trial writing in a power calibration area on the optical disk; an amplitude level calculating unit for obtaining an amplitude level of a reproduction signal which is obtained by reproducing an area in the power calibration area in which the trial writing is performed with the obtained optimum recording power; a memory for storing the obtained optimum recording power and the amplitude level of the reproduction signal; and a comparing unit for comparing a difference between the amplitude level of the reproduction signal stored in the memory and an amplitude level of a reproduction signal which is obtained by reproducing again the area in which the trial writing is performed with the optimum recording power, to a prescribed value, when additional recording is performed on the optical disk; wherein the optimum recording power setting unit performs trial writing in the power calibration area and sets an optimum recording power to be used in the additional recording when the comparing unit decides that the difference exceeds the prescribed value, and sets the optimum recording power stored in the memory as an optimum recording power to be used in the additional recording when the comparing unit decides that the difference does not exceed the prescribed value. Therefore, even when there are changes with time in the pickup of the optical disk recording apparatus, or particularly, dirt or dust are accumulated in the pickup, the optimum recording power can be set again, thereby preventing the recording quality from being deteriorated.
A method for setting an optimum recording power in an optical disk recording apparatus according to a second aspect of the present invention comprises the steps of: obtaining an optimum recording power of a laser diode when data is recorded on an optical disk, by performing trial writing in a power calibration area on the optical disk; obtaining an amplitude level of a reproduction signal which is obtained by reproducing an area in the power calibration area in which the trial writing is performed with the obtained optimum recording power; storing the obtained optimum recording power and the amplitude level in the memory; when additional recording is performed in the optical disk, comparing a difference between the amplitude level of the reproduction signal stored in the memory and an amplitude level of a reproduction signal which is obtained by reproducing again the area in which the trial writing is performed with the optimum recording power, to a prescribed value; performing trial writing in the power calibration area and setting an optimum recording power to be used in the additional recording when it is decided that the difference exceeds the prescribed value; and setting the optimum recording power stored in the memory as an optimum recording power to be used in the additional recording when it is decided that the difference does not exceed the prescribed value. Therefore, effects as those in the first aspect of the present invention are obtained.